Anyone with any experience making carbon bits??

Hi Pabs was a laminator for around 5 years mate
what are you using resin wise epoxy or poly?
too much pig will slow the cure in poly and yer won't see the weave
if memory serves me right you need a special pigment for epoxy
wet lay up I presume
regards Steve B

 

Using black pigment on a carbon fibre lay up will hide the weave pattern, why would you want to do that? You can add up to 10% pigment to epoxy, though with black you can get away with less than that.

 

Pablo, be careful with pigment whatever resin you're using.


Firstly what resin system are you using? Most pigment will mix with epoxy, but you really want the slightest amount, just enough to tint the resin ideally. A little pigment goes a really long way, so unless you're looking to recolour a resin, just go with 0.5 - 1% max.


Are you remaking the battery box or is it some other component you're looking to make?
What weight of material are you using and is it plain weave or twill? You can make it air tight with one ply if you're careful.
Are you trying to make it a sealed unit, if so how is the seal provided and what's the fixing method you're using for your lid / cover?


Have you made any other parts since then? because if you get pinholes in clear resin you'll get them with pigmented resin so you're not achieving anything other than trying to kid yourself that its a better finish. If its just a few pinholes you can sort that out with whats called a resin wipe - easier than a remanufacture.


Lets have some more info and we'll take it from there.

 

Hi.
Interesting to read this as i'm playing with carbon myself. I have the opposite problem if you can call it that. I use so much epoxy that even a single layer is hole free, but not the lightest. I usually try compressing the layers overnight to squeeze out what i can.
Can i ask where you buy supplies from as i'm using CARBONMODS / EASYCOMPOSITES but wonder if i'm missing a trick and paying over the odds.

 

I take it you are not using vacuum bagging then? this will remove excess resin from your layup.

 

Correct. I thought i'd just give the basic wet lay up a go first before spending the extra on vacuuming. Most of what i've been doing is one off brackets and modifications so haven't even made moulds to be able to vac bag properly anyway. It's not too hard though. I'm already quite happy to do what ever i need. One big issue is knowing how many layers to use for a given application.

 

hi Pabs
looking like you are on the right track never had great results with mouldlease seems to work better on old/used moulds
wax and pva the way to go
by the way beleive it or not hairspray works as well as pva and comes in a handy sprayer
pouring warm water down the gap between the mould and part helpes with release,disolves the pva/hairspray
regards Steve B

 

Hey it's looking pretty good really. Were the air pockets you're talking about in the tighter corners? If so i had the same issue. I actually got great improvements by putting a plastics bag inside the mould once the carbon was laid, filling the bag with sand and packing it into all the corners hard, then putting a book on top of the whole lot and compressing it under the bed over night. I see you're mould's larger and deeper than what i was doing but it really did help. And just for info, the plastic bag peeled straight off the part which i wasn't expecting as i just wanted to try the technique. The bag just left a dull finish.
As for releasing the part from mould, i'd wax it like crazy and use the pva release agent. Only ever an issue when i'd used so much epoxy, it sqeezed so far out the mould onto parts i hadn't waxed and stuck to it.

 

You can build up the moulding you have made
no need to do whole new one
Steve

 

Hello again. What ever you do, don't think the fibreglass resin you can buy from halfords will be a quick alternative to buying the correct resin. It isn't. This idiot tried and it goes off so quick one experiment went form not sticking around the mould to rock hard in the space of a minute. The turn time is really fast, very little time sticky. Just fluid, then solid.
I could've made my bin out of carbon if i used the same amount thats been thrown in it.

 

pablo,

You've done some nice work on the pattern, and yes, template everything as its easier to layup that way and you avoid bridging.

One other thing as well is once you've cut your material out, and mixed your resin wet everything out, as then you do two things, firstly you allow the resin to go further and properly wet out the material, secondly you're not racing against time trying to avoid an exotherm. Oh and you probably already know but a paint roller and tray are your friends!

One last thing, if you have templated everything you can do this:
lay out a sheet of release film or clingfilm, or clear bin liner, wet your cloth out and cover in a second sheet so you have a sandwich.
You can then get the roller and really go mental getting air bubbles out and saturating your material properly.

with a marker draw around your templates, and cut out with shears.

now you have backing film on both sides of the cloth, remove one side, lay into mould, and the remove other side - mo fraying edges or strands misbehaving - wet out and work at leisure.

If you want a cheap intensifier, cover your part in cling film, the heavy duty stuff, and lay it into your component with care, ensuring it goes into all the corner and is generous around radii.

then just use some dry matt strips to act as breathers, and chuck the whole lot in a bin liner and then suck it out with a vacuum cleaner. if you've got those bags which allow you to suck down clothes and the like then even better as they'll retain a modicum of vac.

the vacuum clothes bag works with polyester as well, as ultimately you're not maintaining a constant suction which can suck out the styrene.

If you need drill bushes, rivnuts etc. I've got shet loads, just shout, same goes for flash tape and breech couplings.

In fact if you know of any machine shops that want a shed load of drill bushes and rivnuts just shout!

 

If you do have trouble with the weave spreading/moving, i make the first layer a fair bit larger than needed, and fold some gaffer tape round the edges. Keeps the weave in shape, but then plain weave i found more stable than twill anyway. But even saying all that, i've not done a mould your size so it's just things i'm finding which may help at some point. I've done the prewetting too but only ever layed it on a bin bag and peeled it off to use so it wasn't great to handle. The cling film sandwhich i'll try for sure.

 

Hi Pablo, sorry for the delay in getting back.

Yes, in a word. Ideally if the resin that you've painted onto the mould as your surface layer is fully cured then you have a mechanical bond. but, if you can get it at the stage where the resin has cured enough for you to leave a fingerprint witness but not gloop on your finger then what you put onto in will chemically bond.

Great stuff, and remember if you haven't got any acetone cleaner, just let it all cure off and then use a blowtorch to burn the resin away

Ideal. When you use one big piece of cloth over a complex shape, you risk 'bridging'. if you imagine that the cloth doesn't drape fully on the surface of the mould and instead acts like a suspension bridge cord between two high points. this is what gives the pockets in the resin, as there is a void between the material and the mould surface. It's a text book mistake when people come from using chop strand matt to a woven fabric, as the chopped strand matt will break down and you can prod it into the various shapes, whereas a woven matt won't allow you to do that as easily.
You can do it, it comes with experience. The heavier the weight of material, the harder it will be to drape in one hit over a convoluted shape.
Also weave patterns will greatly affect this as well. A twill weave (herringbone pattern) will skew easier than a plain weave (what Ducati like to use), but will drape easier over a bigger area - but you don't need to worry yourself with that at this stage.

If you feel that you can control the first ply, then no, you don't need to do it. Alternatively, try this - paint your first coat of resin on the mould and allow it to go off a little, so it's still goopy, but no longer runny.


put your pre cut but not wetted out templated pieces on the mould - so that the goopiness of the resin actually grips the material. prod it all in to the corners, and then wet it out with brush or roller. That's your first ply (visual ply) down and lovely.


the remaining plies can now be wetted out and placed in the mould in one of several ways:
1) before cutting the patches, place your cloth on a sheet of plastic (bin liner, garden bag, clear liner etc). Wet out the material and place another piece of sheeting on top of it. now you can draw around your templates and cut out the material without it fraying on the edges or distorting.
take off one piece of backing sheet, and lay into mould. Remove the remaining backing sheet and use your roller to make sure its down and get rid of trapped air.


or


2) Paint your next layer of resin on the existing ply. put your templated cloth patch on this. You haven't wetted out, it goes on dry. Use your roller to push the patch home. What you'll see is the resin bleeding through and wetting the cloth as you go.


in both cases, be gentle!


As 1037sp has said, weaves behave differently as well.
Plain weave fabric is easier to control, and also you can get the nice light weights of it - which really help with first plies.
The trade off is that heavier weight plain weaves don't drape as easily as a twill when you start getting to 300gsm and up.

Vacuum bag for duvets is ideal, however be prepared to accept that you'll be throwing the bag away.


When you vacuum bag, you need three things:


Release film - the barrier between your moulded part and the bag. This is what stops the bag from sticking to the back of the carbon. the most common is Halar. Halar comes in three flavours, plain, pin prick, and punched hole. They relate to the surface- in your case you'd want use pin prick as you wan to bleed a controlled amount of excess resin and allow air out of the part.


Breather - The breather is a layer between your release film and the part. look at it as a race track for the air to escape out of, and for resin to bleed off on to. This can be as simple as a bit of cotton, or can be the very expensive bespoke breather blanket materials.
I have used dry matt in the past, or even chopped strand matting.


Vacuum bagging material - when you use this, don't give it the full Lawrence immediately! suck the air out partially, then manoeuvre the bag into any cavities and voids and onto corners and onto surfaces. suck a little bit more out and repeat. eventually you have the bag in all the nooks and crannies and then you can give full suction. What you'll see is the resin bleeding through all the prick holes in the release film and onto the breather. once the bag is sucked down, take the Dyson off and let the part cure. then you can take it out of the bag - which is messy crappy work.


Note - to be safe, your bag needs to be minimum 1.5 times the size of the part you're making - you'll bed surprised how it 'disappears'!
pick off release film and trim your part.


Vacuum Bagging Consumables Supplier - Easy Composites (release film perforated, breather, regular vacuum bagging film - which you can use to wet out your cloth as above.)


Trimming the part


Use a diamond wheel. I use a diamond wheel on a Dremel for small parts, and the barrel abrasives. You'll go through a lot of these!




Any other questions please ask oh, and I'm in that Surrey - A3 corridor